Anode assembly for cathodic protection systems

ABSTRACT

An anode assembly for cathodic protection systems, especially for the cathodic protection of submerged spaced supporting legs of offshore platforms, comprising an elongated carrier cable adapted for spanning the spaced submerged legs of the platform and carrying an elongated anode along the length of the cable intermediate the ends thereof, the anode being spaced from the connecting ends of the cable to provide for substantially uniform current distribution to the platform legs.

United States Patent inventors Edward P. Anderson Livingston, N.J.; PaulB. Byrne, Warren, NJ.; Risque L. Benedict, Upland, Calif.

Appl. No. 882,127

Filed Dec. 4, 1969 Patented Oct. 26, 1971 Assignee Engelhard Minerals 8:Chemicals Corporation ANODE ASSEMBLY FOR CATHODIC PROTECTION SYSTEMS 4Claims, 4 Drawing Figs.

US. Cl 204/196, 204/286, 204/290 F, 204/297 Int. Cl C23f 13/00 Field ofSearch 204/ 147,

References Cited UNITED STATES PATENTS 2,870,079 1/1959 McCall 204/1972,908,623 10/1959 Doring 204/196 3,037,926 6/1962 Ambler 204/1973,342,716 9/1967 Anderson et al 204/196 3,409,530 11/1968 Locke et al.204/196 3,497,443 2/1970 Von Burgsdorfl 204/196 Primary Examiner-T. TungAttorneys-Samuel Kahn and John G. Kovalich ABSTRACT: An anode assemblyfor cathodic protection systems, especially for the cathodic protectionof submerged spaced supporting legs of offshore platforms, comprising anelongated carrier cable adapted for spanning the spaced submerged legsof the platform and carrying an elongated anode along the length of thecable intermediate the ends thereof, the anode being spaced from theconnecting ends of the cable to provide for substantially uniformcurrent distribution to the platform legs.

PATENTEDum 26 Ian SHEET 10F 2 IN VI N'I ()Rfi' EDWARD P /\NI)IYH5ON PAULB, HYRNF HY RISOUE L. BENEDICT 9k 1k. AGENT PAIENTEDum 26 I9?! SHEET 2OF 2 INVIEN'IURS EDWARD P ANDERSON PAUL B, BYRNE BY R/SOUE L BENEDICTANODE ASSEMBLY FOR CATI-IODIC PROTECTION SYSTEMS BACKGROUND OF THEINVENTION An anode mounted on a structure to be cathodically protectedgenerally requires that the anode be insulated from he structure by adielectric shield around the anode location in order to achieve propercurrent distribution to the structure being cathodically protected.Without an adequate dielectric shield area around the anode, the currentdistribution on the cathode surface is not uniform because theresistance through the electrolyte varies considerably from he anodelocation to the more remote areas of the structure being protected.Consequently, the areas of the structure immediately adjacent the anodecould be under more current protection than required while the moreremote areas could be underprotected It was found that if a dielectricmaterial, which was impervious to the severe electrochemical reactionsinherent in cathodic protection, could be applied in a radius of severalfeet around the anode, then it was possible to achieve relativelyuniform current distribution at a considerable distance from each anode,for example, a series of spaced anodes on a ship's hull. It was furtherfound in the cathodic protection of ship hulls that the useful life ofthe dielectric shields is about years or so, but this is not aparticular disadvantage because the ships can be drydocked at 5 yearintervals, or so, and the dielectric shields can be replaced. However,the use of dielectric shields on the submerged legs of offshoreplatforms is a more serious matter because they dont come into drydockand must remain in place for at least about years, which is longer thanthe expected life of any dielectric shield material known to date forcathodic protection purposes. Therefore, the present inventioncontemplates the provision of an active anode remotely positioned fromthe surfaces being cathodically protected with the elimination of anyneed for a dielectric shield on the surfaces being protected.

SUMMARY OF THE INVENTION The invention deals with an anode for cathodicprotection systems, especially for the cathodic protection of submergedspaced supporting legs of offshore platforms, comprising an elongatedcarrier cable adapted for spanning the spaced submerged legs, anelongated electrical conductor positioned adjacent to and along thelength of the cable, an electrically conductive clamp means clamping thecarrier cable and the electrical conductor in parallel spacedrelationship and in electrical contact with the electrical conductor,the cable, conductor and clamp means being embedded in an elongated massof insulation material, an electrically conductive member, e.g. anipple, extending from the clamp through the insulation material, and anelongated anode, e.g. a wire, mounted on the external surface of theinsulation material along the length thereof and electrically connectedto the electrically conductive member.

DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an exaggeratedelevational schematic view of an offshore platform incorporating theanode assembly of the invention,

FIG. 2 illustrates an elevational side view of the anode assembly of theinvention,

FIG. 3 illustrates a cross-sectional view along lines 3-3 of FIG. 2, and

FIG. 4 illustrates a partly elevational and partly brokenaway side viewof a clamp according to the invention including a carrier cable andelectrical conductor clamped therein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I is an exaggeratedschematic view of an offshore platform I carrying on its upper surfaceworking structures such as derrick 2 and housing 3. The platform I issupported above the ocean surface 4 by a plurality of spaced metal legsof which legs 5 and 6 are shown rising upwardly from the ocean floor 7.The legs, e.g. legs 5 and 6, are cathodically protected by means of theanode assembly of the invention generally designated as 8 and whichcomprises an elongated carrier cable 9 spanning the spaced submergedlegs and connected to connectors such as eyebolts l0 and 11 each mountedon a submerged leg. The carrier cable carries an electrical conductor 12which leads to the cathodic protection power system (not shown) on theplatform. The cable also carries elongated anodes I3 and I4 such as wireanodes, along the length of the cable intermediate the ends thereof, theanode being spaced from the connecting ends of the carrier cable toprovide for substantially uniform current distribution to the platformlegs.

FIGS. 2 to 4 show the particular anode assembly according to theinvention, which comprises the elongated carrier cable 9 adapted forspanning the spaced submerged legs of an offshore platform, or otherstructures supported by spacedapart submerged metal legs. The assemblyfurther comprises an insulated electrical conductor I2 positionedadjacent to and lengthwise of the cable. The cable 9 and conductor I2are clamped together in parallel spaced relationship by means of anelectrically conductive clamp means generally designated by the numeralIS. The clamp, for purpose of illustration, is shown as of rectangularconfiguration, but it may also be of substantially cylindricalconfiguration. As illustrated, the clamp 15 is composed of a pair ofmating clamp sections I6 and 17 each channelled on one surface as at 18,I9 and 20, 21, respectively, each of semicircular cross section, so thatwhen the channelled surfaces are positioned adjacent each other theycooperate to form passages of substantially circular cross section forembracing the cable 9 and conductor I2 passing therethrough. Asillustrated by FIG. 2, the assembly is provided with a plurality ofclamps I5 spaced from each other lengthwise of the cable 9 and conductorI2 with the cable and conductor mounted therein as illustrated by FIGS.3 and 4. Both the carrier cable 9 and conductor 12 are shown as having acore composed of a plurality of wires 22 and 23, respectively, with thecores being covered by insulation material 24 and 25, respectively. Oneof the clamp sections 16 is provided with an electrically conductivenipple 26 extending outwardly thereof, and the channels I9 and 21 are ofreduced cross section intermediate their ends so that when assembled, asillustrated by FIG. 4, they form a throat 27 intermediate the ends ofthe channels. In order that current may be transmitted to conductiveclamp 15, the insulation 25 of conductor I2 is stripped off at thelocation of throat 27 whereby the throat is in electrical contact withthe wires 23 of conductor I2. When the two clamp sections I6 and I7 areassembled with the cable 9 and conductor I2 mounted therebetween asillustrated by FIG. 4, the clamp sections are secured together by meansof bolts or screws 28, 29 and 30 as illustrated. Having clamped thecarrier cable 9 and conductor I2 according to FIG. 4, with the conductorin electrical contact with the clamp IS, the cable 9, conductor 12 andthe clamp 15 are embedded in an elongated mass of insulation material 3Ie.g. neoprene, as by molding, over a length intermediate the ends 32 and33 of the carrier cable 9, but with the nipple 26 extending from theclamp 15 through the insulation leaning its end portion 34 exposedthrough the insulation 31. The nipple 26 is an efi'ective electricallyconductive member between the clamp 15 and the elongated anodehereinafter more particularly described. As illustrated by FIG. 2, theends 32 and 33 of the carrier cable 9 are provided with hooks 35 and 36,respectively, for mounting the cable on connectors 10 and ll of the legs5 and 6 and thereby spanning the legs as illustrated in FIG. I.

Having embedded the cable, conductor and clamp as described above at alocation intermediate the ends of the cable, one or more elongatedanodes I3 and I4, e.g. in the form of wire, are mounted on andlengthwise of the surface of the elongated insulation mass 3], e.g. acylindrical mass. When a plurality of anodes are employed they arespaced from each other along the length of the insulation mass M. Theanodes are positioned in electrical contact with the exposed ends 34 ofthe nipples 26 and secured thereto bolts 37 as illustrated by FIGS.effective securing means may be employed. Preferably, the anode wires,as illustrated, are composed of a titanium, niobium or tantalum wirehaving spaced platinum sleeves 38 mounted thereon along the lengththereof. A plurality of retaining rings 39 of insulation resin materialare mounted along the length of the insulation mass 31 to retain theanode against the surface of the mass or cylinder 31. A tubing 40 of thesame material is advantageously used to retain the end portions of theanode.

As above described, the invention contemplates the provision of an anoderemotely positioned from the surfaces being cathodically protected toprovide for substantially uniform current distribution. In order toeffect the uniform current distribution, the anodes are located on theinsulation mass 3] intermediate the ends of the carrier cable withopposite portions of the cable from the location of the ends of theanode to the ends of the cable each being at least as long as the lengthof the wire anode, or the combined length of a plurality of anodes whena plurality of anodes as illustrated by FIG. 2 are employed. Forexample, if the anode or combined anodes employed lengthwise of thecable have a length of about 40 feet, then the opposite portions of thecable leading from the vicinity of ends of the anodes to ends of thecable would each have a length of about 60 feet.

Various modifications of the invention within the scope of the appendedclaims.

by means of securing 2 and 3. However, any other are contemplated Weclaim:

I. An anode assembly for cathodic protection systems comprising anelongated carrier cable having opposite ends, an elongated electricalconductor positioned adjacent to and along the length of the cable, thecable and conductor being embedded in an elongated mass of insulationmaterial along a portion thereof intermediate the opposite ends of thecable, an electrically conductive means in electrical contact with theelectrical conductor and extending through the elongated mass ofinsulation material, the electrically conductive means comprising anelectrically conductive clamp embedded in said insulation material andclamping the cable and the electrical conductor in parallel spacedrelationship, and an elongated anode mounted on the external surface ofthe insulation material along the length thereof and electricallyconnected to the electrically conductive member.

2. An anode assembly according to claim 1, wherein said electricallyconductive clamp comprises an electrically conductive nipple extendingthrough the insulation material.

3. An anode assembly according to claim 1, wherein the elongated anodeis a wire anode composed of titanium, niobium or tantalum having spacedplatinum sleeves mounted thereon along the length thereof.

4. An anode assembly according to claim 1, wherein opposite portions ofthe cable from the ends of the anode to the ends of the cable are atleast as long as the length of the anode.

2. An anode assembly according to claim 1, wherein said electricallyconductive clamp comprises an electrically conductive nipple extendingThrough the insulation material.
 3. An anode assembly according to claim1, wherein the elongated anode is a wire anode composed of titanium,niobium or tantalum having spaced platinum sleeves mounted thereon alongthe length thereof.
 4. An anode assembly according to claim 1, whereinopposite portions of the cable from the ends of the anode to the ends ofthe cable are at least as long as the length of the anode.